1. Field of the Invention
The invention relates generally to the fields of immunology, microbiology and inflammatory bowel disease and more specifically to the diagnosis and treatment of inflammatory bowel disease using microbial antigens.
2. Background Information
Inflammatory bowel disease (IBD) is the collective term used to describe two gastrointestinal disorders of unknown etiology: Crohn's disease (CD) and ulcerative colitis (UC). The course and prognosis of IBD, which occurs world-wide and is reported to afflict as many as two million people, varies widely. Onset of IBD is predominantly in young adulthood with diarrhea, abdominal pain, and fever the three most common presenting symptoms. The diarrhea may range from mild to severe, and anemia and weight loss are additional common signs of IBD. Ten percent to fifteen percent of all patients with IBD will require surgery over a ten year period. In addition, patients with IBD are at increased risk for the development of intestinal cancer. Reports of an increased occurrence of psychological problems, including anxiety and depression, are perhaps not surprising symptoms of what is often a debilitating disease that strikes people in the prime of life.
Unfortunately, the available therapies for inflammatory bowel disease are few, and both diagnosis and treatment have been hampered by a lack of knowledge regarding the etiology of the disease. What is clear, however, is that a combination of genetic factors, exogenous triggers and endogenous microflora can contribute to the immune-mediated damage to the intestinal mucosa seen in inflammatory bowel disease. In Crohn's disease, bacteria have been implicated in initiation and progression of the disease: the intestinal inflammation in Crohn's disease is notable for its frequent responsiveness to antibiotics and susceptibility to bacterial fecal flow. Common intestinal colonists and novel pathogens have been implicated in Crohn's by direct detection or by disease associated anti-microbial immune responses. Furthermore, in many genetically susceptible animal models of chronic colitis, lumenal micro-organisms are a necessary cofactor for disease; animals housed in a germ-free environment do not develop colitis. However, despite much direct and indirect evidence for a role for enteric microorganisms in Crohn's disease, the pathogenic organisms and antigens contributing to the immune dysregulation seen in this disease have not been identified.
Current diagnostic assays for Crohn's disease are unable to detect all patients with the disease. Thus, identification of novel microbial antigens associated with Crohn's disease would provide reagents that can increase the sensitivity of current diagnostic assays. In addition, such microbial antigens can bear a disease related T-cell epitope and, as original or contributing inducers of the disease-related immune response, can be effective tolerogenic antigens for treating inflammatory bowel disease. Identification of IBD-associated microbial antigens also would facilitate isolation of the involved microbial species, paving the way for the discovery of new antibiotics or drugs for treating inflammatory bowel disease, such drugs ameliorating disease by eliminating the microbial inducers of disease.
Thus, there is a need for identification and isolation of microbial IBD-associated antigens for diagnosing and treating the many individuals suffering from inflammatory bowel disease. The present invention satisfies this need by providing the IBD-associated I-1 and I-2 microbial antigens. Related advantages are provided as well.